CN114855033A - High-elongation aluminum alloy and preparation method thereof - Google Patents

Abstract

The invention relates to the technical field of aluminum alloy materials, and discloses a high-elongation aluminum alloy and a preparation method thereof, wherein the high-elongation aluminum alloy comprises the following raw materials in percentage by mass: 6 to 8 percent of silicon, 0.15 to 0.3 percent of magnesium, 0.4 to 1 percent of manganese, less than or equal to 0.15 percent of iron, 0.01 to 0.03 percent of strontium, 0.1 to 0.25 percent of lanthanum-cerium mixture, and the balance of aluminum and inevitable impurities. The scheme optimizes and configures metal elements in the aluminum alloy, controls the content of Fe in the alloy and reduces the brittle needle-like FeAl ₃ The content of the aluminum alloy material is increased, so that the plasticity of the alloy material is improved; the content of Mg is controlled, and the Mn element is used for compensating the Mg element, so that the reduction of the elongation of the alloy material due to the overhigh content of the Mg is avoided. In addition, by adding different kinds of rare earth elements, the rare earth is utilized to purify harmful impurity elements and refine grains, so that the purpose of fine grain strengthening is achieved, and meanwhile, the method also has the advantages of adding different kinds of rare earth elements, purifying harmful impurity elements and refining grainsEffectively changes the compound form of iron-rich multi-element intermetallic compounds in the die-casting aluminum alloy, thereby obviously improving the elongation of the alloy material.

Description

A kind of high elongation aluminum alloy and preparation method thereof

technical field

The invention relates to the technical field of aluminum alloy materials, in particular to a high elongation aluminum alloy and a preparation method thereof.

Background technique

Aluminum alloy has the characteristics of low density, high specific strength and specific stiffness, good corrosion resistance, excellent electrical and thermal conductivity, easy recycling, and good low temperature performance. It is widely used in transportation, aerospace, electronic appliances and other fields. With the increasingly fierce competition in the automotive market, aluminum alloys have low density, high strength, especially some even surpass high-quality steel, good plasticity, and can be processed into various types of materials. Corrosion and other characteristics make aluminum alloy parts one of the commonly used materials for automobiles. For example, the existing battery separators are all made of AlSi7Mg aluminum alloy, which is welded in the aluminum alloy frame to separate the batteries, so as to prevent the batteries from being squeezed and cracked when the car is impacted, resulting in safety hazards such as explosions.

In terms of mass fraction percentage, the existing AlSi7Mg aluminum alloy contains: Si6.5～7.5%, Mg0.45～0.7%, Ti0.1～0.2%, Mn≤0.1%, Fe≤0.19%, Cu≤0.05%, Zn≤0.07%, the balance is aluminum and inevitable impurities; its elongation ≥7%, with low ductility. Due to the low elongation of the above-mentioned AlSi7Mg aluminum alloy, in the actual forming process of the bottom plate of the battery tray, due to the phenomenon of thermal expansion and contraction, the battery separator is prone to cracking after the impact test on the aluminum alloy due to the phenomenon of thermal expansion and contraction. The mechanical property requirements of high elongation cannot be met, resulting in safety hazards. Therefore, there is an urgent need to develop a high elongation aluminum alloy with an elongation greater than 10%.

SUMMARY OF THE INVENTION

The present invention is intended to provide a high elongation aluminum alloy to solve the technical problem of low elongation of existing aluminum alloy materials.

In order to achieve the above purpose, the present invention adopts the following technical scheme: a high elongation aluminum alloy, comprising the following raw materials by mass fraction: silicon 6%-8%, magnesium 0.15%-0.3%, manganese 0.4-1%, iron≤0.15 %, strontium 0.01-0.03%, lanthanum-cerium mixture 0.1-0.25%, the balance is aluminum and inevitable impurities.

The principle and advantages of this scheme are:

1. Compared with the AlSi7Mg aluminum alloy in the prior art, the aluminum alloy material obtained in this scheme has lower magnesium and iron content by optimizing the allocation of metal elements in the alloy; such as controlling the content of Fe in the alloy, reducing the brittle needle-like FeAl ₃ content can eliminate the harmful effects of Fe, especially reduce the splitting effect of acicular compounds on the die-casting aluminum alloy matrix, significantly increase the elongation of the aluminum alloy material, and improve the plasticity of the alloy material; control the Mg content and compensate by the Mn element Mg element, to avoid the reduction of elongation due to excessive Mg content; through the above effects, the aluminum alloy material prepared by the present invention not only has high thermal conductivity and excellent mechanical properties, but also has high elongation.

2. The present invention optimizes the alloy composition and structure by adding different kinds of rare earth elements, uses rare earth to purify harmful impurity elements, refines grains, and achieves the purpose of fine grain strengthening, and at the same time, it also effectively changes the iron-rich multi-metal in the die-casting aluminum alloy. Compound form; for example, mixed lanthanum-cerium rare earth added in an appropriate amount has the functions of refining, purifying molten aluminum, and refining the structure, and mixed rare earth and Si, Fe, etc. coexist at the grain boundaries to form a Si-Fe eutectic structure and improve aluminum. The morphology of the Si-Fe eutectic structure in the alloy changes the morphology of the Si-Fe eutectic from a coarse needle-like shape to a fine fibrous shape, which effectively improves the strength of the alloy; if an appropriate amount of strontium is added, it can effectively change the die-casting The Si eutectic morphology in the aluminum alloy can effectively improve the elongation of the material. The applicant's research proves that the lanthanum, cerium, rare earth elements and strontium elements in this solution play a synergistic role in the prepared aluminum alloy, and jointly improve the elongation of the aluminum alloy, so that the elongation of the obtained aluminum alloy is ≥ 11.4%, which is significantly The phenomenon that the aluminum alloy material in the prior art is prone to punching cracking due to low elongation is improved, and thus has a potential safety hazard.

Preferably, the mixing ratio of lanthanum-cerium in the lanthanum-cerium mixture is lanthanum:cerium=7:3. Using the above scheme, the two rare earths of lanthanum and cerium are mixed into rare earth mixture in advance, so that when preparing the aluminum alloy material, a sufficient amount of the lanthanum, cerium and rare earth mixture reacts with the aluminum alloy raw material ferrosilicon to form the Si-Fe eutectic structure, which effectively changes the die-casting aluminum alloy. The eutectic morphology of Si and Fe in the alloy can effectively improve the elongation of the material.

Preferably, the weight of the impurities is less than or equal to 0.5%, including raw materials with the following mass fractions: titanium 0.11-0.16%, calcium ≤ 0.0009%, phosphorus ≤ 0.04%, beryllium ≤ 0.0001%, zinc ≤ 0.04%, tin ≤ 0.04%, lead ≤0.04%, nickel≤0.04%, chromium≤0.04%. The above scheme can significantly reduce the influence of impurities on aluminum alloy materials. For example, calcium and Ca can react with P, Si and other elements to form high-melting compounds. These compounds will reduce the fluidity and feeding performance of the alloy; at the same time, the presence of Ca will also lead to The rupture of the A1 ₂ 0 ₃ film increases the hydrogen content of the molten aluminum and the probability of pores and shrinkage in the casting, thereby affecting the surface and internal quality of the product.

A preparation method of high elongation aluminum alloy, comprising the following steps:

S1: melting, melting industrial pure aluminum to obtain melt I;

S2: feeding and degassing, adding raw materials silicon, magnesium, manganese and strontium to the melt I obtained in S1 in turn, heating and stirring to melt to obtain melt II;

S3: refining and slag removal, adding a refining agent to the melt II obtained in S2, stirring to remove the slag, and obtaining a melt III;

S4: degassing and slag removal, adding lanthanum-cerium mixture and refining agent to the melt III obtained in S3, stirring for degassing and slag removal to obtain melt IV;

S5: transfer die casting, transfer the melt IV obtained in S4 for transfer die casting to obtain an aluminum alloy casting.

The principle and advantages of this scheme:

1. This scheme controls the Mg content and compensates the Mg element with the Mn content to improve the elongation of the aluminum alloy product. In addition, Mn can prevent the recrystallization process of aluminum alloys, increase the recrystallization temperature, can effectively inhibit the occurrence of the recrystallization process of aluminum alloys, and can effectively improve the strength of aluminum alloys; moreover, Mn can effectively disperse by forming _MnAl6 compounds with Al. The particles hinder the growth of recrystallized grains, thereby refining the internal grains of the aluminum alloy, thereby greatly increasing the elongation of the aluminum alloy. Another function of MnAl ₆ is to dissolve impurity iron (Fe) and form (Fe, Mn)Al ₆ , which makes the flake or needle-like structure formed by iron in the aluminum alloy into a fine crystal structure and reduces the harmful effects of iron. influences.

2. This scheme effectively ensures the uniformity and purity of the aluminum alloy melt by adding raw materials in batches for refining, degassing and slag removal, thereby effectively improving the elongation and other service properties of the prepared aluminum alloy, and improving the aluminum alloy yield rate. .

Preferably, in S1, it also includes the detection of iron and impurity content; in S2 and S3, it also includes the detection of raw material content and the stage of feeding melting; slag; in S5, before the melt IV is transported and die-casting, the detection of the melt density is also included, and the melt density is greater than or equal to 2.58 g/ml.

Using the above scheme, the content of raw materials in the melt is monitored in real time and the amount of raw materials missing after refining and slagging is supplemented. The main reason is that the impurities in the raw materials are removed, which makes the content of metal elements in the raw materials deviate in the melt. If the element content is low, it needs to be melted and added by feeding; and after each feeding is melted, the newly added impurities in the melt are refined, degassed, and slag removed, which effectively ensures the quality of the melt and improves the quality of the melt. The quality of aluminum alloy products makes aluminum alloy products have higher strength, such as its specific strength is close to that of high alloy steel, its specific stiffness exceeds that of steel, it has good casting properties and plastic workability, good electrical and thermal conductivity, and good corrosion resistance. properties and solderability.

Preferably, in S1, the melting temperature is 650°C-750°C; in S2, the melting temperature is 760°C-820°C; in S2 and S3, the feeding melting temperature is 700°C-750°C °C. By adopting the above scheme, the melting temperature is set according to the melting properties of different raw materials, which effectively saves production costs and improves production efficiency.

Preferably, the refining agent includes the following raw materials in parts by mass: 18-24 parts of sodium nitrate, 5-10 parts of potassium fluorotitanate, 33-41 parts of potassium chloride, 15-20 parts of zinc chloride, and sodium sulfate 3-8 parts, phosphorus pentachloride 10-15 parts, sodium fluoroborate 12-18 parts, aluminum fluoride 8-14 parts, calcium carbonate 16-22 parts, charcoal powder 10-15 parts. By adopting the above scheme, the raw material of the refining agent is simple and the production cost is reduced; and the refining agent of this scheme effectively removes the impurities of each raw material, and obtains a melt with higher purity, thereby improving the strength and service performance of the aluminum alloy product.

Preferably, in S3 and S4, the added amount of the refining agent is 0.1-0.3% by weight of the melt, and the refining time is 20-30 min. By adopting the above scheme, the addition of other impurities due to the addition of a large amount of refining agent in the prior art can be effectively avoided, thereby affecting the strength and other properties of the aluminum alloy product.

Preferably, in S2, the stirring is specifically performed at a rotational speed of 500 to 550 rpm, followed by stirring for 5 to 8 minutes, followed by standing for 10 minutes, and repeated stirring and standing for three times; in S4, the stirring is specifically performed at a rotational speed of 500 rpm. Stir for 5-8 min at ~550 rpm. With the above scheme, low-speed stirring can effectively avoid safety problems caused by melt splashing; at the same time, it is conducive to the stirring and dispersion of materials in the melt, and finally achieve sufficient and efficient dispersion of sufficient materials in the melt.

Preferably, in S2-S4, nitrogen gas is introduced into the melt while the stirring is performed, and the nitrogen flow rate is 22-28L/min; in S2 and S3, the nitrogen pressure is 0.2-0.5MPa, and in S4 , the nitrogen pressure is 0.4-0.6MPa. By adopting the above scheme, it is convenient for the bubbles in the melt to be collected and discharged with nitrogen during the stirring process, so as to achieve the purpose of removing the gas in the melt.

Description of drawings

1 is a process flow diagram of a method for preparing a high elongation aluminum alloy in an embodiment of the present invention.

FIG. 2 is a graphical graph of the elongation test run of the aluminum alloy in Example 4 of the present invention.

Detailed ways

The following is further described in detail by specific embodiments:

Example 1

Table 1 shows the differences in aluminum alloy raw materials and contents between Examples 1 to 5 and Comparative Examples 1 to 3 (existing AlSi7Mg). Taking Example 1 as an example, the raw material composition and preparation process of a high elongation aluminum alloy are described.

A high elongation aluminum alloy, the raw materials of the following mass fractions: silicon (Si) 6%-8%, magnesium (Mg) 0.15%-0.3%, manganese (Mn) 0.4-1%, iron (Fe)≤0.15% , strontium (Sr) 0.01-0.03%, lanthanum-cerium (La-Ce) mixture 0.1-0.25%, the balance is aluminum and inevitable impurities; impurity weight ≤ 0.5%, including the following mass fraction of raw materials: titanium (Ti) 0.11～0.16%, calcium (Ca)≤0.0009%, phosphorus (P)≤0.04%, beryllium (Be)≤0.0001%, zinc (Zn)≤0.04%, tin (Sn)≤0.04%, lead (Pb)≤ 0.04%, nickel (Ni)≤0.04%, chromium (Cr)≤0.04%.

The composition and percentage content of each element in this embodiment specifically include: silicon 8%, magnesium 0.3%, manganese 0.88%, iron 0.15%, strontium 0.025%, lanthanum-cerium mixture 0.2% (the ratio of lanthanum-cerium is lanthanum:cerium=7:3 ), impurities ≤ 0.5%, and the balance is aluminum.

The present invention also provides a preparation method of high elongation aluminum alloy, the preparation process is shown in Figure 1, and the specific preparation steps are as follows:

S1: material preparation and melting: prepare raw materials by mass percentage, and heat industrial pure aluminum to 700°C (optional temperature range is 650°C to 750°C) to melt to obtain melt I;

Sampling melt I for spectral analysis, and measure the element content in melt I, including the content of each auxiliary material (silicon, manganese, magnesium, strontium), Fe and other impurities, and control the content of Fe and other impurities in a small range ( Fe≤0.15%, impurities≤0.5%);

S2: feeding and degassing: adding silicon, manganese, magnesium and strontium to the melt I obtained in S1 in turn for alloying, heating to 760°C-820°C, stirring at 500-550 rpm for 5 minutes, stirring and then letting stand Stir again for 10 min, wherein stirring and standing are cycled three times in total to obtain melt II. During the stirring process, nitrogen gas was introduced into the melt, and the nitrogen pressure was 0.2-0.5 MPa.

Sampling melt II for spectral analysis to determine the element content in melt II, mainly detecting the content of silicon, manganese, magnesium and strontium. The amount of raw materials missing after refining and slag removal can effectively ensure the quality of aluminum alloy products; and after each feeding is melted, the newly added impurities in the melt are refined, degassed, and slag removed. Effectively ensure the quality of the melt, and then improve the quality of the aluminum alloy products, so that the aluminum alloy products have higher strength, such as its specific strength is close to that of high alloy steel, its specific stiffness exceeds that of steel, it has good casting performance and plastic workability, and good electrical conductivity. , thermal conductivity, good corrosion resistance and solderability.

S3: Refining and slag removal: Add a refining agent to the melt II obtained in S2, and the amount of the refining agent is 0.1-0.3% by weight of the melt, stir for 20-30 minutes under the nitrogen pressure of 0.2-0.5MPa, and then statically Set for 15 to 20 minutes, and obtain melt III after full slag removal and degassing.

The refining agent contains the following raw materials by weight: 15-25 parts of sodium chloride, 15-25 parts of potassium chloride, 3-10 parts of sodium fluorosilicate, 2-5 parts of sodium hexafluoroaluminate, and 5-5 parts of sodium carbonate. 15 parts, 3 to 10 parts of calcium fluoride; this scheme specifically includes 20 parts of sodium chloride, 20 parts of potassium chloride, 5 parts of sodium fluorosilicate, 3 parts of sodium hexafluoroaluminate, 10 parts of sodium carbonate, fluoride 5 parts of calcium, the above raw materials are mixed to prepare a white powder refining agent, ≥98% of the particles in the refining agent can pass through a 1mm standard sieve. The refining agent is mainly used to remove the hydrogen and floating oxidation slag in the molten aluminum to make the melt more pure.

Sampling melt III for spectroscopic analysis to determine the element content in melt III, mainly detecting the content of silicon, manganese, magnesium and strontium, after feeding, melt at 700 ° C ~ 750 ° C, and repeat step S3, for feeding The melt obtained after melting is refined again to complete deslagging and degassing.

S4: Degassing and slag removal, adding lanthanum-cerium mixture and refining agent to the melt III obtained in S3, the amount of refining agent added is 0.1-0.3% of the melt weight, the nitrogen pressure is 0.4-0.6 MPa, and the nitrogen flow rate is 22 Under the condition of ~28L/min, stir for 5-8min, and after stirring, let stand for 10min and stir again, wherein stirring and standstill are cycled three times in total to obtain melt IV.

S5: transfer die casting, sample and test the melt IV obtained in S4, when the density of the melt IV is greater than or equal to 2.58g/ml, it is recorded as qualified, and then transfer the melt IV for die casting to prepare an aluminum alloy product.

When sampling and testing, when the density of melt IV is less than or equal to 2.58g/ml, it is recorded as unqualified, and the preparation needs to be restarted.

Table 1 Differences in raw material content of the aluminum alloys obtained from Examples 1 to 5 and Comparative Examples 1 to 3

In the preparation process of the high elongation aluminum alloy of this scheme, the amount of impurity elements is within the range described in the claims (impurity weight ≤ 0.5%, including raw materials with the following mass fractions: titanium 0.11-0.16%, calcium ≤ 0.0009%, phosphorus ≤0.04%, beryllium≤0.0001%, zinc≤0.04%, tin≤0.04%, lead≤0.04%, nickel≤0.04%, chromium≤0.04%), the amount of refining agent raw materials is within the scope of the claims (chlorinated ≤0.04%) 15-25 parts of sodium, 15-25 parts of potassium chloride, 3-10 parts of sodium fluorosilicate, 2-5 parts of sodium hexafluoroaluminate, 5-15 parts of sodium carbonate, 3-10 parts of calcium fluoride) High elongation aluminum alloys are obtained, and the elongations of the obtained high elongation aluminum alloys are all above 11.4. And in the reaction steps S1-S5, the melting temperature of aluminum is 650°C-750°C, the melting temperature of auxiliary materials is 760°C-820°C, the melting temperature of supplementary material is 700°C-750°C, the amount of refining agent added is 0.1-0.3%, and the refining time is 0.1-0.3%. An aluminum alloy with an elongation higher than 11.4 can be obtained under any combination of conditions ranging from 20 to 30 min. Since the elongation of the aluminum alloy prepared by selecting the conditions described in different claims does not change much, only one of the combined reaction conditions is selected to illustrate the influence of different raw material contents on the properties of the aluminum alloy obtained by this scheme.

Test example: aluminum alloy performance test

The tensile strength, yield strength and elongation of the aluminum alloys obtained in Examples 1 to 5 and Comparative Examples 1 to 3 were respectively tested, and the test results are shown in Table 2 and FIG. 2 .

Table 2 Performance testing results of the aluminum alloys obtained in Examples 1-5 and Comparative Examples 1-3

From the test data in Table 2, it can be seen that compared with AlSi7Mg aluminum alloy, the aluminum alloy profiles obtained in this scheme have a significant improvement in tensile strength, yield strength and elongation. 122Mpa, elongation ≥11.4%, significantly higher than the performance of the existing AlSi7Mg aluminum alloy (the tensile strength of the aluminum alloy obtained in Comparative Example 3 is 240Mpa, the yield strength is 106MPa, and the elongation is 7.5%); it shows that the Mn element can compensate The adverse effect of Mg element on the elongation of aluminum alloy. While comparing Example 3 (the elongation of the aluminum alloy obtained in Example 3 was 12.7%) and Example 4 (the elongation of the aluminum alloy obtained in Example 4 was 14.2%, Figure 2 shows the graph of the aluminum alloy elongation test run. It can be seen from the curve diagram) that when the content of other elements is controlled and the preparation process is unchanged, excessive substitution of Mn element for Mg element will reduce the elongation of the prepared aluminum alloy. Only by properly controlling the Mg content, Mg is compensated by Mn element. Elements can effectively avoid the problems of high strength and low elongation caused by excessive Mg content, thereby significantly improving the elongation of aluminum alloys.

The aluminum alloy material obtained in this scheme has lower magnesium and iron content by optimizing the configuration of metal elements in the alloy; for example, controlling the content of Fe in the alloy, reducing the content of brittle needle-like FeAl ₃ , eliminating the harmful effects of Fe, especially reducing the The needle-like compound has a splitting effect on the die-casting aluminum alloy matrix, which significantly improves the elongation of the aluminum alloy material and the plasticity of the alloy material. The demand for aluminum alloy profiles with high elongation.

And compared with Comparative Examples 1 and 2 without rare earth elements added, the aluminum alloy prepared by adding lanthanum cerium rare earth mixture to the raw material of the aluminum alloy of this scheme has higher elongation and better strength properties. It is because by adding different kinds of rare earth elements, the alloy composition and structure can be optimized; rare earth elements can achieve the purpose of fine grain strengthening by purifying harmful impurity elements, refining grains, etc., and at the same time effectively changing the iron-rich multi-metal intermetallic in die-casting aluminum alloys. compound form. For example, an appropriate amount of mixed lanthanum-cerium rare earth (Examples 1 to 5) is added, because the rare earth element has the functions of refining, purifying molten aluminum, and refining the grain structure, and the mixed rare earth and Si, Fe, etc. coexist at the grain boundary, forming The Si-Fe eutectic structure improves the morphology of the Si-Fe eutectic structure in the aluminum alloy, and the morphology of the Si-Fe eutectic is transformed from a coarse needle flake shape to a fine fiber shape, which effectively improves the strength of the alloy. In addition, by comparing Examples 1 to 5 with Comparative Example 2, it can be seen that adding an appropriate amount of strontium element can effectively change the Si eutectic morphology in the die-casting aluminum alloy, thereby effectively improving the elongation of the material. The applicant's research proves that the lanthanum, cerium, rare earth elements and strontium elements in this solution play a synergistic role in the prepared aluminum alloy, and jointly improve the elongation of the aluminum alloy, so that the elongation of the aluminum alloy obtained in Examples 1 to 5 is improved. ≥11.4%, which significantly improves the safety hazard phenomenon that the aluminum alloy material is prone to punching cracks due to low elongation in the prior art.

The above are only examples of the present invention, and common knowledge such as well-known specific technical solutions and/or characteristics in the solutions are not described too much here. It should be pointed out that for those skilled in the art, some modifications and improvements can be made without departing from the technical solution of the present invention, which should also be regarded as the protection scope of the present invention, and these will not affect the implementation of the present invention. effect and the applicability of the patent. The scope of protection claimed in this application shall be based on the content of the claims, and the descriptions of the specific implementation manners in the description can be used to interpret the content of the claims.

Claims (10)

1. A high elongation aluminum alloy characterized by: the material comprises the following raw materials in percentage by mass: 6 to 8 percent of silicon, 0.15 to 0.3 percent of magnesium, 0.4 to 1 percent of manganese, less than or equal to 0.15 percent of iron, 0.01 to 0.03 percent of strontium, 0.1 to 0.25 percent of lanthanum-cerium mixture, and the balance of aluminum and inevitable impurities.

2. The high elongation aluminum alloy of claim 1, wherein: the mixing ratio of lanthanum to cerium in the lanthanum-cerium mixture is 7: 3.

3. The high elongation aluminum alloy of claim 2 wherein: the weight of the impurities is less than or equal to 0.5 percent, and the impurities comprise the following raw materials in percentage by mass: 0.11 to 0.16 percent of titanium, less than or equal to 0.0009 percent of calcium, less than or equal to 0.04 percent of phosphorus, less than or equal to 0.0001 percent of beryllium, less than or equal to 0.04 percent of zinc, less than or equal to 0.04 percent of tin, less than or equal to 0.04 percent of lead, less than or equal to 0.04 percent of nickel and less than or equal to 0.04 percent of chromium.

4. A method of producing a high elongation aluminium alloy according to any one of claims 1 to 3, wherein: the method comprises the following steps:

s1: melting, namely melting the industrial pure aluminum to obtain a melt I;

s2: adding materials and degassing, sequentially adding raw materials of silicon, magnesium, manganese and strontium into the melt I obtained in the step S1, heating, stirring and melting to obtain a melt II;

s3: refining and deslagging, namely adding a refining agent into the melt II obtained in the step S2, and stirring and deslagging to obtain a melt III;

s4: degassing and deslagging, namely adding a lanthanum-cerium mixture and a refining agent into the melt III obtained in the step S3, and stirring, degassing and deslagging to obtain a melt IV;

s5: and (4) transferring and die-casting, wherein the melt IV obtained in the step S4 is transferred and die-cast to obtain an aluminum alloy casting.

5. The method of claim 4, wherein the method comprises the following steps: in S1, detecting the content of iron and impurities; in S2 and S3, a raw material content detection and feeding melting stage is also included; adding a refining agent to stir, degas and remove slag every time feeding and melting are carried out; in S5, the melt IV is detected before transferring and die casting, and the melt density is more than or equal to 2.58 g/ml.

6. The method of claim 5, wherein the method comprises the following steps: in S1, the melting temperature is 650 ℃ to 750 ℃; in S2, the melting temperature is 760 ℃ to 820 ℃; in S2 and S3, the feed melting temperature is 700 ℃ to 750 ℃.

7. The method of claim 6, wherein the method comprises the following steps: the refining agent comprises the following raw materials in parts by weight: 15-25 parts of sodium chloride, 15-25 parts of potassium chloride, 3-10 parts of sodium fluosilicate, 2-5 parts of sodium hexafluoroaluminate, 5-15 parts of sodium carbonate and 3-10 parts of calcium fluoride.

8. The method of claim 7, wherein the method comprises the steps of: in S3 and S4, the addition amount of the refining agent is 0.1-0.3% of the weight of the melt, and the refining time is 20-30 min.

9. The method of claim 8, wherein the method comprises the steps of: in S2, the stirring is specifically stirring for 5-8 min at the rotating speed of 500-550 rpm, standing for 10min, and repeatedly stirring and standing for three times; in S4, the stirring is specifically carried out for 5-8 min under the condition that the rotating speed is 500-550 rpm.

10. The method of claim 9, wherein the method comprises the steps of: in S2-S4, nitrogen is introduced into the melt while stirring, and the flow rate of the nitrogen is 22-28L/min; the nitrogen pressure is 0.2-0.5 MPa in S2 and S3, and 0.4-0.6 MPa in S4.

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